Cross reference is made to the following application filed concurrently herewith: application Ser. No. 09/723,084 entitled xe2x80x9cBlade Cleaning Systemxe2x80x9d by Bruce E. Thayer et al.
The present invention is directed to toner dispensing apparatus. More specifically, the present invention is directed to toner dispensing apparatus for a developer station in an automatic electrostatographic machine.
In the act of xerography a photoconductive insulating plate supported by conductive backing is first uniformly charged, and then exposed to a light and shadow image to be reproduced. Under the influence of the light image the photoconductive layer becomes conductive and the charge is selectively dissipated in the light image areas through the photoconductive plate to the conductive backing leaving an electrostatic latent image on the photoconductive plate. The electrostatic latent image which is not visible to the eye is made visible by contacting the photoconductive plate bearing the image with a finely divided pigmented resin base material commonly referred to in the art as toner which is first charged to an appropriate potential such that the toner will adhere to the photoconductive plate in the image or charged areas for a charged area development system.
Typically the developer is transferred from the photoconductive plate to a final support material such as paper and fixed such as by heat fusing thereto to form a permanent record of the original.
In an automatic reproducing device, the toner material is consumed in the development process and it must be periodically replaced within the development system in order to sustain continuous operation of the machine. Various techniques have been used in the past to replenish the toner supply. Initially new toner material was added directly from supply bottles or containers to the dispensing apparatus by pouring.
Attempts have been made to provide a separate toner hopper with a dispensing mechanism for adding the toner from the hopper to the developer apparatus in the automatic xerographic reproducing machines on a regular or as needed basis.
The toner dispensing mechanism has been widely used. Some dispensing mechanisms employ an open celled foam dispensing roll, the toner is loaded into the cells during that portion of the foam roll""s travel in the toner hopper. As the foam roll is rotated past the two sets of lobes, the toner is retained under pressure within the open cells of the foam roll. As the foam roll is rotated past the exit lobe the release of the pressure on the open cells provides a spring thrust to the toner within the cells so that a force in addition to that of gravity expels the toner out of the cells into the developer chamber.
While this technique is generally satisfactory, it suffers from certain drawbacks. With continued use and particularly with long term use, the open celled foam roll gradually becomes impregnated with toner often times with the toner impregnation extending all the way to the foam roll shaft. As the foam roll becomes increasingly impregnated, several things happen to the operational properties under which the foam dispensing roll operates. Initially, as the toner impregnation commences the foam tends to lose flexibility or resiliency and therefore lacks that extra kick to expel toner from the open cells of the foam to the developer chamber. The toner not expelled from the cells contributes to the further buildup or impaction of toner in the open cells of the foam roll.
This gradual buildup also contributes to non-uniform and generally decreasing toner dispensing rates until it reaches a point where the foam roll is fully impregnated with toner and the dispensing rate falls off drastically leading to nonuniform image density from copy to copy. In addition, as the degree of toner impregnation or compaction of the foam roll increases, the outside diameter of the foam roll decreases to a point where the seal between the roll and the hopper lobes is lost and undesirable large amounts of toner may pass to the developer chamber. Furthermore, as the foam roll becomes impregnated with toner the torque required to drive the roll increases, increasing the load on the motor driving the shaft and/or increasing the load on the shaft. In this instance it is possible for the shaft to fracture or separate from the foam and/or the motor to burn out. In each of the above instances, the operational life of the dispensing roll is substantially reduced and it must be replaced at unscheduled times giving rise to increased service cost for the reproducing machine user.
It is an object of the present invention to provide a novel toner dispensing apparatus without any moving parts.
There is provided a toner dispensing apparatus for dispensing toner to a station, including a toner hopper for containing a quantity of finely divided toner, said hopper having an elongated opening formed by the cooperation of the walls thereof through which toner is capable of being dispensed from said hopper, and a dispensing electrode array on a surface of one of said walls, for transporting toner in a direction of movement toward said elongated opening at a dispensing rate; and a wave generator for generating a traveling wave pattern for transporting toner in said direction of movement.
For a better understanding of the present invention as well as other objects and further features thereof, reference is made to the following description of the invention to be read in conjunction with the accompanying drawings wherein: